Secondary schools across Scotland had a total of 2,992 English teachers in 2008, but by last year that had fallen to 2,473 – a drop of 519.
Meanwhile the number of maths teachers declined from 2,787 to 2,364 over the same period – a fall of 423.
Scottish Conservative education spokeswoman Liz Smith said: “Parents will be very angry when they see this evidence of the decline in teacher numbers, especially in core subjects like English and maths.”
Figures on teacher numbers, published by the Scottish Government, showed the number of French language teachers in secondary schools also plummeted from 1,070 in 2008 to 688 in 2018.
At the same time the number of teachers whose main subject is German dropped from 180 to 90, although the number primarily teaching Spanish went from 64 to 119.
Ms Smith said the decline in teacher numbers in some subjects “comes at the same time as many people in education are expressing their deep-seated concern about the reduction in subject choice”.
She said: “It is completely unacceptable that the SNP has allowed this situation to develop.
“They were warned about the implications several years ago and ministers have done nothing to address the problem. Meanwhile, young people in our classrooms are losing out on vital education.”